When the group exits the elevator, Moore is missing from the shot of them exiting it, simply appearing at the table in the shot after.
Denholm Elliot is pointing a gun at Tom Baker but under voodoo influence turns the gun on himself so that it's pointing at the middle of his head. An impossible move . The camera then looks down the barrel and the position of the hands have changed allowing for the gun position which wouldn't have been possible under the influence.
(at around 57 mins) The first thing seen in the voodoo hut is a mask obviously meant to be of Haitian origin, though it's actually of Pacific Northwestern Native American origin.
In the POV close ups of the gun that Diltant uses to shoot himself, you can see that it's barrel is plugged.
Maitland lights a match in his coffin and it goes out, but there is still light in the coffin.
When Daniel Massey leaves his sister's residence to go to the restaurant, you can see people watching the filming from their upstairs windows.
Once all are in the vault, Harold comments that there is no way out, although nobody has looked behind the wall hangings.